Process and apparatus for continuously removing contaminants from edible cooking oil

ABSTRACT

In accordance with the present invention a process and apparatus for removing contaminates from edible cooking oil is provided. A continuous stream of cooking oil at an elevated temperature is withdrawn from a cooking bath. A continuous stream of liquid solvent for at least a portion of the contaminates is mixed with the oil. The solvent has a specific gravity different than the specific gravity of the oil. As the oil and solvent streams are mixed, at least a portion of the contaminates are transferred from the oil to the solvent. The oil and solvent mixture is then separated by specific gravity into a stream comprising cleaned oil and a stream comprising solvent and contaminates. The cleaned oil stream is then returned to the bath, preferably being heated in a heat exchanger prior to introduction in the bath.

This is a divisional of copending application Ser. No. 205,215 filed onJune 10, 1988, now U.S. Pat. No. 5,008,122.

BACKGROUND OF THE INVENTION

(1) Field of the Invention

The present invention relates to a process and apparatus for removingcontaminates from edible cooking oil. More particularly, the presentinvention relates to a process and apparatus for continuouslywithdrawing a continuous stream of hot edible cooking oil from a cookingbath, removing at least a portion of contaminates in the cooking oil andthereafter returning the cleaned cooking oil to the bath.

The present invention also relates to a process for cooking comestiblessuch as nuts in an edible oil bath and continuously maintaining thequality of oil in the bath during the cooking process by withdrawing acontinuous stream of the oil, cleaning the oil and returning it to thebath.

(2) Description of the Prior Art

During the cooking of comestibles in oil, and in particular in thecooking of snack foods in oil, the cooking oil becomes contaminated withsubstances transferred from the comestibles being cooked into the hotoil.

In the processing of edible nuts which are conventionally packaged andsold as snack-type products, nuts such as peanuts, cashews, almonds,walnuts, filberts, macadamia nuts, pecans and the like are coated withsugars and/or adhesive solutions for adhering the sugars to the nut.These sugars may comprise sucrose, corn syrup, honey, fructose or anynumber of sugars used in the coating of nuts and are transferred to theoil bath during oil roasting of the coated nuts. In addition, anadhesive, particularly a carbohydrate adhesive, may be used to adherethe sugars to the coated nut during roasting, and gum may be transferredto the oil bath during or roasting of the nuts.

The coated nuts are roasted at process temperatures of between about250° and about 400° F. During roasting the coating comprising sugar willbecome tacky and some of the coating will transfer to the oil. As thecoating particles are maintained in the oil, they will begin tocarbonize and/or carmelize, thus contaminating the cooking oil. In ashort period of time the oil becomes unsuitable for cooking nuts becausethe taste and coloration of the nuts falls outside of desired processstandards. More particularly, the carbonized or carmelized sugar coatingmay adhere to the tack coated nuts as they move through the oil and thetaste of the nuts is adversely affected. Moreover, the oil bath darkensto a point where the nuts produced are darkened outside of desiredprocess standards.

In addition, the process equipment can become fouled with the carbonand/or carmelized sugar coating transferred to the oil during thecooking process. Thus, as the oil degrades, the entire system andproduction line must be shut down to clean the nut roasting apparatusand remove the cooking oil and replace it with additional cooking oil.The additional cooking oil must be reheated to process temperaturesbefore the process can be started. The down time for cleaning andreplacement of the oil is a substantial factor in the cost of theproduct. The output of the equipment is reduced substantially bycontamination of the oil and fouling of the equipment, therebyincreasing the need for additional lines, which in turn requiressubstantial capital expenditure. Moreover, during the course of theprocess, as the cooking oil degrades, the quality of the product variesover the life of a particular oil bath. The quality of the product maybe inconsistent due to oil degradation.

The temperature of the oil during processing is between about 250° F.and 400° F. and is difficult to clean during the continuous cooking ofthe comestibles in the oil bath. In a conventional oil bath, the oil iscontinuously circulated through a mesh filter which screens some of thelarger particulate matter. In a case where nuts including a coatingcomprising sugars are processed, the screen can become clogged. Even ifthe screen is not clogged, the oil still degrades due to the fine natureof the sugars, which pass through the mesh filter.

It would be desirable to maintain oil quality thoughout the cookingprocess to thereby maintain a substantially uniform quality of thecomestibles being cooked. It is also desirable to maintain theprocessing equipment in a clean condition. Through maintenance of theoil quality and maintenance of equipment in a clean condition,production can be increased or maximized by reducing process shutdowntime. By reducing shutdown, the capacity of the equipment is increased,and the requirement for additional capital expenditures for additionalequipment may, in some instances, be reduced or avoided.

SUMMARY OF THE INVENTION

In accordance with the present invention a process and apparatus forremoving contaminates from edible cooking oil is provided. A continuousstream of cooking oil at an elevated temperature is withdrawn from acooking bath. A continuous stream of liquid solvent for at least aportion of the contaminates is mixed with the oil. The solvent has aspecific gravity different than the specific gravity of the oil. As theoil and solvent streams are mixed, at least a portion of thecontaminates are transferred from the oil to the solvent. The oil andsolvent mixture is then separated by specific gravity into a streamcomprising cleaned oil and a stream comprising solvent and contaminates.The cleaned oil stream is than returned to the bath, preferably beingheated in a heat exchanger prior to introduction in the bath.

In accordance with one aspect of the invention, the liquid solvent andthe hot oil are mixed under a pressure sufficient to substantiallyinhibit vaporization of the liquid solvent which is preferably water.When the oil and solvent are mixed, the mixture has an elevatedtemperature which enhances the solubility of the contaminates in thesolvent. In the instance where a contaminate is sucrose and the solventis water the amount of sucrose which will dissolve in water having anelevated temperature is substantially greater. Moreover, it is believedthat the dissolution of the sucrose is the water occurs more rapidly inwater having an elevated temperature. These dissolution factors areadvantageous in a process for continuously removing the sucrose from theoil. By maintaining the mixture at a pressure sufficient tosubstantially inhibit vaporization of the solvent, the mixing of solventand hot oil in atmospheric conditions and the attendant vaporization andbubbling of the hot oil is avoided.

In accordance with one aspect of the invention, the mixture of oil andsolvent is separated in of a centrifugal contactor which continuouslyreceives the oil and solvent, and continuously separates the mixtureinto a stream of cleaned oil and a stream comprising solvent andcontaminates.

In accordance with one aspect of the invention, after the oil has beenseparated from the solvent, trace amounts of solvent may still exist inthe cleaned oil, and it is desirable to permit the oil to come toatmospheric pressure in a flash chamber to vaporize the solventThereafter, the cleaned oil is returned to the cooking bath, preferablythrough a heat exchanger that elevates the temperature of the oil to thebath temperature.

The quality of the oil is maintained through removal of thecontaminates, and the cooking equipment is maintained in cleancondition. The down time of the equipment is reduced substantially, andthe standard of quality of the comestible product is maintained at asubstantially uniformed level, and particularly at a quality level whichis much more consistent than in a conventional process. The hot oil issafely cleaned by maintaining the pressure of the mixture of the cookingoil and solvent at a level sufficient to inhibit vaporization of thesolvent. Thus, the danger of mixing hot oil with a solvent issubstantially reduced or eliminated.

Additional advantages of a process and apparatus in accordance with thepresent invention will be described in the detailed description of theinvention with reference to the drawings, and such description follows.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic of an apparatus for continuously removingcontaminates from cooking oil;

FIG. 2 is a sectional view of a portion of a centrifugal contactor;

FIG. 3 is a sectional schematic view of the centrifugal contactor shownin FIG. 2 wherein an oil stream and a solvent stream are separatelyintroduced into the centrifugal contactor; and

FIG. 4 is a sectional schematic view of the centrifugal contactor shownin FIG. 2 wherein a stream comprising a mixture of the oil stream andthe solvent stream is introduced into the centrifugal contactor.

DETAILED DESCRIPTION OF THE INVENTION

In accordance with the present invention, as shown in FIG. 1 comestiblesare subjected to oil at an elevated temperature in oil bath 10. Thecooking operation can be conducted on a batch or a continuous basis inan oil bath 10. In the case of a continuous oil roasting operation foroil roasting of nuts, a continuous web of wire mesh fabric fromstainless steel or the like and transported on a continuous basis movesthrough the bath 10. Contaminates from the comestible are transferred tothe oil bath.

Oil is withdrawn from the oil bath 10 and passed through a conventionalscreen 12 which removes large particles, pieces of comestibles and otherobjects larger than the openings in the screen. The main pump 15circulates oil through a heat exchanger 14 which maintains thetemperature of the oil at a desired level. Oil which has passed throughthe heat exchanger 14 is then returned to the oil bath 10 throughconduit 16.

Contaminated oil is withdrawn through conduit 18 by a centrifugal pump20 which pulls the contaminated oil through a strainer 22. Manual valves24 and 26 permit the user to decide whether to direct the contaminatedoil through the centrifugal pump 20 or through a parallel conduit 28which permits the oil to be pumped under the power of the main pump 15rather under the power of the centrifugal pump 20. The pressure andtemperature of the oil are monitored by pressure gauge 30 andtemperature gauge 32. A pressure transducer 34 permits the pressure tobe monitored by electrical means and fed into computing apparatus, notshown, which may control the entire system.

At various stages of the process, manual valves are positioned in theconduits so that flow may be controlled or stopped at any point alongthe process. The manual control valve is indicated by a particularsymbol, v and manual control valves will hereinafter be given referencecharacter 36.

The contaminated oil flows through a rotameter 38 which measures thevolume flow rate of the oil passing through the conduit Thereafter, theoil moves through a fluid flow control valve 40 which measures thevolume flow of fluid therethrough and adjusts a control valve 42. Acheck valve 44 permits flow of the contaminated oil in a singledirection. The oil conduit 46 is joined with a conduit 48 which suppliesthe solvent for the contaminates.

The oil/solvent mixture passes through conduit 50. The pressure andtemperature of the mixture is measured by pressure and temperaturegauges 52 and 54. A resistance temperature device 56 and a pressuretransducer may be used and connected to a computing system. Becausecontactor 60 vibrates, the conduit 50 is connected to the contactor 60via a flexible conduit 62.

The contactor 60, which will be described in detail hereinafter,separates the oil and solvent mixture into a stream comprising cleanedoil and a stream comprising solvent and contaminates. As will bedescribed in detail, the contactor separates the oil and the solvent bygravity separation. The cleaned oil exits the contactor via conduit 64and flows through a flexible conduit 66, a one-way check valve 68, amanual valve 36, and a control valve 70 which is controlled by apressure transducer 72. The cleaned oil conduit also includes aresistance temperature device 74, a temperature gauge 76 and a pressuregauge 78. A pressure control valve 80 is positioned in the conduit forregulation of the pressure. The cleaned oil flows through a sight glass82, through a manual valve 36 and then to a flash chamber 84. Once theoil reaches the flash chamber, the pressure of the cleaned oil ispermitted to reach atmospheric pressure, and trace amounts of solventare vaporized. The cleaned oil is then returned to a screen 12 whichenters the loop of the oil bath. The cleaned oil is mixed with oil fromthe bath at the screen and then pumped once again through main pump 15.

The conduit for supplying the solvent to be mixed with the oil will nowbe described. Preferably, the solvent comprises washwater 90 introducedfrom a common source of water. The tap water is preferably at roomtemperature and proceeds through manual valves 36 through either acentrifugal pump 92 which pulls the water through a screen 94 or througha parallel line 96 which is supplied under the pressure of tap water.The pressure and temperature of the water is measured by gauges 96 and98. Also, a pressure transducer 100, measures the pressure of the waterand communicates such pressure to a computing mechanism. The water thenpasses through a rotameter 102 and a fluid flow meter 104 which controlsa control valve 106. The water then passes through a manual valve 36 andcheck valve 108 and is thereafter mixed with the stream of oil. Itshould be understood that the oil and water are mixed by a confluence ofconduits 46 and 48 which merge into conduit 50. It is also possible tomix the oil and water streams in a separate mixing chamber provided.

As mentioned previously, the contactor 60 separates the mixture of oiland solvent into a cleaned oil stream which leaves the contactor throughconduit 64 and a stream of solvent and contaminates which leaves thecontactor through a conduit 110. The solvent and contaminate mixturepasses through a flexible conduit 112 and a one-way check valve 114.

If desired, the temperature of the water with contaminates can bereduced by mixing an additional quenching water through conduit 116. Thewater which has been quenched passes through conduit 117 where itspressure is measured by gauge 118. The water passes through a manualvalve 36 and through a check valve 120 which is controlled by a pressuretransducer 122. The water temperature is tested by a resistancetemperature device 124. The pressure and temperature of the water ismeasured by gauges 126 and 128. The water than flows through a pressurecontrol valve 130 the water moves through a sight glass 132 and isdischarged by a valve 36 which may be manually controlled.

At various locations in the apparatus, the sample of the fluid may beremoved via a conduit labeled sample and controlled by a manual controlvalve 36.

The quenching water conduit 140 supplies quenching water through a valve36, a rotameter 142 and a flow meter 144 which controls control valve146. The water passes through a manual valve 36 and through a one-waycheck valve 148 into conduit 116 and is in turn mixed with water at anelevated temperature which comes from contactor 60.

Referring to FIGS. 2-4, the centrifugal contactor utilized in theequipment and process of the present invention and is a conventionalcentrifugal separating device such as that described in "Advances InCentrifugal Extraction", Chemical Engineering Progress, (Volume 61, No.5, May, 1965; "Multiple Functions In A Centrifgual Extractor", ChemicalEngineering Progress, (Volume 62, No. 8, August, 1966); and, "ImprovingPerformance of Centrifugal Extractors", Chemical Engineering, July 24,1972. Essentially, the contactor includes a means for placing liquidshaving different specific gravities in the contactor, rotating thecontactor at relatively high speeds, and separating the liquid having ahigher specific gravity from a liquid having a lower specific gravity. Aconventional contactor, as shown in FIG. 2, includes a body 150 whichrotates about an axis 152. The contactor includes an internal chamber154 having a plurality of baffles 156 for separating and mixing theliquid in the chamber 154. The contactor includes two inlet ports 158and 160. The contactor also includes an exit port 162 for relativelyheavy liquids and has an exit port 164 for relatively light liquids. Inthe case of the contactor shown in FIG. 1, only one inlet port is usedbecause the oil and solvent are mixed prior to introduction into thecontactor.

During the course of operation of the contactor, the oil, which has aspecific gravity less than water, exits through exit port 164 whereasthe water exits through port 162. The port 162 corresponds to conduit110 in FIG. 1. The exit port 164 corresponds with conduit 64 in FIG. 1.

As shown schematically in FIG. 4, the oil and the water mixture 170 isdirected into cavity 154. As the contactor rotates, the oil is driven tothe interior of the chamber 154 and through an outlet port. The cleanedoil is indicated at reference character 172. The solvent containingcontaminates is heavier and moves to radially outwardly. The solvent andcontaminates are indicated at 174.

Referring to FIGS. 2 and 3, an alternative form of the invention isshown wherein the water 178 is introduced through conduit 158 and theoil 180 is introduced through conduit 160. The contactor serves not onlyas a separator but also as a contactor and mixer. As the oil movesthrough the water, the contaminates and the oil are transferred to thewater and preferably become soluble in the water. The water andcontaminates exit through exit port 162 to provide a stream ofcontaminated solvent 182. The cleaned oil stream exits through port 164to provide a cleaned oil stream 184.

As can be appreciated from reviewing FIGS. 1-4, the oil at an elevatedtemperature is maintained at a pressure above atmospheric pressure whenit is mixed with the water, during separation in the contactor, andduring egress from the contactor until the cleaned oil reaches a flashchamber, where trace of amounts of the water can be safely vaporizedfrom the oil.

A process for roasting nuts in accordance with the present inventionwill now be described in greater detail so that the advantages of asystem according to the present invention can be understood. First, itis necessary to describe the process for preparing the nuts prior toroasting. The comestibles which are processed in accordance with theinvention can be any food which is roasted, fried or otherwise cooked inhot oil and, in particular, edible nuts which are conventionallypackaged and sold as snack-type products or which are utilized fordecoration and as fillers in the confectionery and baked foods industry.Illustrative of such nut-meats are peanuts, cashews, almonds, walnuts,filberts, macadamia nuts, pecans, and the like. Particularly preferredproducts provided in accordance with the invention are those derivedusing peanuts and cashews as the starting materials.

The nuts are deshelled in a preliminary step and, optionally, may alsobe subjected to other conventional procedures such as blanching and thelike prior to being subjected to the process of the invention. The term"raw nuts" is used hereinafter to refer to nuts in the form in whichthey are subjected to the first step of the process of the inventionirrespective of what preliminary treatment, if any, has been applied tothe nuts. Thus, nuts which have been subjected to a process to remove aportion of their fat content are included within the meaning of thisterm.

The raw nuts are subjected to coating with an adhesive solutioncontaining honey. The nut products prepared according to the presentinvention are, thus, honey-roasted because it is this adhesive solutioncontaining honey which actually transfers the heat to the nuts to effectroasting, whether the coated nuts are roasted by immersion in oil (oilroasting) or by air convection (dry roasting).

The coating is accomplished in a conventional coating drum. The nuts areintroduced into the drum and an appropriate amount of the adhesivesolution is introduced while providing agitation by rotating the drum atan appropriate speed until the nuts are uniformly coated with a layer ofthe adhesive solution. Alternatively, and preferably, particularly whenthe process is carried out on a continuous basis as described more fullyhereafter, the nuts and the adhesive solution are introducedsimultaneously in the appropriate proportions, and rotation of the drumis carried out as before until uniform coating is achieved. In general,the adhesive solution is employed in a proportion in the range of about5 parts by weight to about 10 parts by weight, and preferably in therange of about 6 parts by weight to about 8 parts by weight, per 100parts by weight of nuts.

The adhesive solution preferably comprises a mixture of honey, cornsyrup, sucrose, a carbohydrate gum and water. Advantageously, theproportion of these components lies within the following ranges (allpercentages by weight of total mixture).

Honey: 10 to 40 percent

Corn Syrup: 10 to 40 percent

Sucrose: 10 to 40 percent

Water: 10 to 20 percent

Carbohydrate Gum: 0 to 1.0 percent

The percentage of water expressed above and hereafter is preferably theproportions of the above components lie within the following ranges ofpercentages by weight:

Honey: 25 to 30 percent

Corn Syrup: 25 to 30 percent

Sucrose: 25 to 30 percent

Water: 12 to 16 percent

Carbohydrate Gum: 0.05 to 0.20 percent

In a particularly preferred embodiment the proportions in percentages byweight of the honey, corn syrup and sucrose are substantially identicaland are of the order of about 27 to 29 percent by weight, the balance ofthe adhesive solution being water.

Other optional additives may be present in the adhesive solution inminor amounts, generally less than about 10 percent by weight of thetotal solution. Illustratively, natural or derived carbohydrate gumssuch as xanthan gum, gum arabic, guar gum, locust bean gum and the likecan-be present in the adhesive solution in amounts up to about 1.0percent by weight. Preferably, xanthan gum will be employed at a levelof about 0.10 to 0.14 percent.

The adhesive solution is preferably prepared by first preparing anaqueous mixture of the xanthan or other gum and then blending this withthe honey and corn syrup and the sucrose, preferably in the form of afruit granular grade. The resulting mixture is then heated withagitation to a temperature of the order of about 150° F. to about 180°F. and preferably about 160° F. to about 170° until complete solution isachieved. If desired, the heating of the syrup can be continued at asufficiently high temperature to remove some of the water and increasethe viscosity and or specific gravity of the adhesive solution to anydesired value. Advantageously, the viscosity of the adhesive solution iswithin the range of about 1200 to about 1800 cps as measured on aBrookfield RVT helipath viscometer using a number 1 spindle. Thespecific gravity of the adhesive solution is advantageously within therange of about 1.27 to about 1.28.

After the nuts have been uniformly coated with the adhesive solution themanner described above, they are then subjected to a second coatingoperation in which they are enrobed with dry particulate sugar. Thiscoating can be applied using conventional coating means such as thecoating drum described above in regard to the first coating step.Indeed, the second coating operation can be carried out immediatelyafter the first coating operation is completed and while the nuts arestill present in the coating apparatus employed therefor.

The two coating operations may be carried out sequentially in a singlecoating drum which is inclined and/or provided with means such as ahelical auger for advancing the nuts along the length of the drum as thelatter is rotated. The adhesive solution is applied to the nuts in afirst zone of such a device and after the nuts have been uniformlycoated, the dry granular sugar is introduced in a second zone of thedevice. The residence time of the nuts in such a coating device isadjusted, advantageously by adjusting the speed of rotation of the drumand the propulsion means, so as to provide adequate time for eachcoating to be accomplished uniformly and completely.

Any of the commonly used forms of granulated sugar can be employed inthis second coating step. Illustrative of such sugars are number Xpowdered sugar. Advantageously, the sugar employed preferably has anaverage particle size from about 40 to about 140 US mesh.

The dry granular sugar is applied to the adhesive coated nuts in aproportion which is advantageously in the range of about 6 to about 12parts per 100 parts by weight of nuts, and preferably within the rangeof about 8 to about 10 parts per 100 parts by weight of nuts.

When the second coating operation has been completed, the coated nutsare roasted in an edible oil such as refined peanut oil at a temperaturein the range of about 300° F. to about 330° F., preferably from about315° F. to about 325° F., and for a time which will vary depending uponthe particular type of nut being processed and upon the temperature ofroasting and the degree of roasting desired Illustratively, the time andextent of roasting will be greater in the case of peanuts (from about4.5 to about 7 minutes) than in the case of cashews (from about 1.5 toabout 3.5 minutes). The most appropriate roasting conditions to beadopted in any particular instance can be determined readily by aprocess of trial and error.

The roasting operation can be conducted on a batch or continuous basis.Referring to FIG. 1, in the case of continuous oil roasting operationthe nuts are retained on a continuous web of wire mesh fabricated fromstainless steel or the like and transported on a continuous basisthrough a bath 10 of the edible oil heated to a temperature within therange set forth above. The residence time of the nuts in the bath isadjusted to provide the desired time of roasting. The roasted nuts,Whether roasted on a continuous or batch basis, are then passed to thefinal coating stage of the process of the invention. Preferably, anyexcess oil remaining on the nuts after the roasting step has beencompleted is allowed to drain off before subjecting the roasted nuts tothis final coating stage.

During roasting, the combined coating on the nuts will become tacky andthis tackiness is used to advantage to adhere a final coating mixture tothe nuts. In the final coating stage, a dry mixture of sucrose and saltis applied to the nuts to provide a uniform coating thereon. Thisoperation is accomplished using any conventional coating means, such asthose described above, and is carried out in a continuous or in a batchprocedure, preferably, shortly after the roasting step.

The dry mixture employed in this coating operation advantageouslycomprises from about 2 to about 3 parts, and preferably about 21/2 partsby weight of sucrose to each part of salt. Any of the forms of sucroseavailable commercially can be employed. Sucrose of the grade known asfruit granular has been found to be particularly adapted for use in thedry mixture employed in this stage. The salt is also preferably of finegranulation, the grade known as flour salt being suitable. The drymixture advantageously has a particle size of about 40 US mesh to about140 US mesh.

The proportions in which the dry mixture of sucrose and salt are appliedin this final coating step are advantageously in the range of about 4parts to about 6 parts and preferably from about 5.0 parts to about 5.5parts by weight per 100 parts by weight of nuts.

When the final coating operation has been completed the resulting coatedand oil roasted nuts are cooled or allowed to cool, if necessary, toambient temperature and then packaged in any appropriate manner fordelivery to the ultimate consumer.

As can be appreciated, during the roasting, a portion of the coating istransferred into the oil bath and contaminates the bath. Also as can beappreciated, in a conventional continuous roasting operation, the nutsare retained on a continuous mesh fabricated from stainless steel, andthe mesh may become clogged with materials from the coating. In aconventional roasting operation, it is necessary to maintain the surfacecolor of the nuts at a reasonably uniform level. More specifically, asthe nuts are processed in accordance with the prior art process, as theoil bath becomes contaminated with carbonized coating and/or carmelizedcoatings, the surface color of the nuts degrades to a point where theproduct is no longer satisfactory. Such degradation can occur within aslittle as four hours of processing time. If the bath reaches a level ofcontamination wherein the surface color of the nuts is no longeracceptable, the entire bath must be emptied and cleaned, requiring asubstantial down time. In accordance with a process of the presentinvention, it has been found that the surface color of the nuts can bemaintained at a consistent level for an excess of 18 hours, therebylengthening the life of the oil bath. One of the benefits of a processin accordance with the present invention, is that the nuts have asurface coloration which is within consistent desirable ranges.Moreover, the useful life of the bath is much longer than previouslyobtained, and the processing equipment has substantially more productioncapability because of the reduced down time. In addition, substantialresources are saved because the equipment does not become fouled duringoperation.

In accordance with one aspect of the invention, it is particularlypreferred that the solvent for the contaminates in the oil beconventional tap water. However, it should be understood that ifdesired, additives can be placed in the water to extend the life of thebath. In particular, and on occasions, it is a concern that the oil maybecome rancid, and may be desirable to add to the solvent alkali thatremoves fatty acids formed during cooking. Other additives can be addedto the water and/or oil if desired.

The solvent and oil are preferably blended so that the solvent comprisesbetween about five and about thirty volume percent solvent However, itshould be understood, that the particular ratio of solvent to oil willbe determined in the particular process for removal of contaminates. Inaccordance with the present invention, the oil at an elevatedtemperature from the bath has a temperature between about 250° F. andabout 400° F., and has a pressure in the range of about 100 psig to 200psig, preferably between about 120 to about 190 psig. The washwater isfurnished at room temperature, generally between about 60° and about 90°F., and has a pressure between about 100 and about 130 psig, preferablybetween about 115 to about 125 psig. The mixture of the water and oilhas a pressure between about 80 and 115 psig and a temperature between200° and 250° F. The cleaned oil after separation from the water has atemperature of between about 225° and about 240° F. and a pressurebetween about 60 and about 80 psig. The water has a temperature betweenabout 150° and about 180° F. and a pressure of about 40 to 50 psig.However, it should be understood that the temperatures and pressures ofthe water and oil may vary depending upon the particular process andrequirement to control flow rates through the contacter.

It should be understood that although specific embodiments of theinvention have been described herein in detail, such description is forpurposes of illustration only and modifications may be made thereto bythose skilled in the art within the scope of the invention.

What is claimed is:
 1. An apparatus for continuously removingcontaminates from edible oil in the cooking bath having a temperature inexcess of 250° F., comprising:a pump for withdrawing a continuous streamcomprising oil and contaminates from said bath, said pump directing saidcontaminated oil through a closed conduit to maintain said oil underpressure substantially in excess of atmospheric pressure; a source ofliquid solvent for at least a portion of said contaminates, said solventcomprising water and having a specific gravity different than thespecific gravity of said oil; means for generating a continuous streamof said solvent, said solvent stream being transferred through aconduit; means for mixing said continuous contaminated oil stream andsaid continuous solvent stream to provide a continuous oil and solventmixture stream, said mixture stream being maintained at a pressuresubstantially above atmospheric pressure to inhibit vaporization of saidsolvent; a centrifugal separator for separating said oil and solventmixture stream by specific gravity into a stream comprising cleaned oiland a stream comprising solvent and contaminates; means for reducing thepressure of the cleaned oil stream to a pressure lower than thevaporization pressure of said solvent to permit any solvent remaining inthe cleaned oil stream to vaporize; means for returning said cleaned oilstream to said bath; and means for discarding said stream comprisingsolvent and contaminants.
 2. An apparatus according to claim 1 andfurther including a check valve in said oil conduit, the pump and saidcheck valve maintaining said oil stream at a pressure between about 100and about 200 psig and at a temperature in excess of about 250° F., saidmeans for generating a continuous stream of solvent comprising a pumpfor said solvent stream and a check valve in said solvent conduit tomaintain said solvent stream at a temperature of between about 60° F.and about 90° F. and at a pressure between about 100 and 150 psig, andcheck valves located downstream of said separator for maintaining saidmixture stream at a temperature between about 150° F. and about 250° F.and at a pressure between about 80 and 115 psig.
 3. An apparatusaccording to claim 2 and further including control means for mixing saidoil stream and said solvent stream in a volume flow ratio of betweenabout 1% and 40% solvent.
 4. An apparatus according to claim 3 whereinsaid volume flow ratio is between about 5% and about 30% solvent.
 5. Anapparatus according to claim 1 wherein said centrifugal separator has acentral zone, said mixture being continuously introduced in said centralzone, a port for removing said solvent stream form one of said zones,and a port for removing said oil stream from the other of said zones. 6.A process according to claim 1 wherein said centrifugal separator has acentral zone, a radially inward zone and a radially outward zone, saidoil stream being introduced in said outward zone, and said solvent beingintroduced in said inward zone, said cleaned oil being removed from saidinward zone and said solvent being removed from said outward zone.